n.1. in concept formation, the best or average exemplar of a category. For example, the prototypical bird is some kind of mental average of all the different kinds of birds of which a person has knowledge or with which a person has had experience. 2. more generally, an object, event, or person that is held to be typical of a category and comes to represent or stand for that category. See prototype model. 3. an early model of something that represents or demonstrates its final form. —prototypal, prototypical, or prototypicadj.